Add travis support

[chrisharper]

I've made some additions and alterations in order for delayed_job to be ran on TravisCI ( http://travis-ci.org/ ).

All that is required is a new service hook being created ( http://about.travis-ci.org/docs/user/getting-started/ ) for the project.

You can also change the ruby selection and update notification preferences using the .travis.yml file ( http://about.travis-ci.org/docs/user/build-configuration/ )

There appears to be an issue with 3.1 activerecord and ruby 1.9.2 ( most likely YAML based) : http://travis-ci.org/#!/chrisharper/delayed_job/builds/88921

P.S I have created a picture of me in a monkey suit to persuade you :
https://twitter.com/#!/_chrisharper/status/104528543744139264

[chrisharper]

UPDATE

After applying the pull request here :#46

It fixes the 3.1 issues on 1.8.7 and rbx : http://travis-ci.org/#!/chrisharper/delayed_job/builds/88948

Jruby with 3.1 seems to still be affected.